Apparatus for heating fluids



March 17, 1942 J. w. 'rHRocKMoRToN E-rm.

v APPARATUS FOR HEATING FLUIDS Filed March' 24, 1941 INV ENTORS.

Patented Mar. 17, 1942 APPARATUS ron HEATING rLUTDs John W. Throckmorton, Wilton, and John S. Wallis, Darien, Conn., assignors to Petro-Chem Development Company, New York, N. Y., a corporation of Delaware application March 24, 1941, serial No. 384,892

(ci. 12a-333) Claims.

Our invention relates to apparatus for heating fluids and more particularly for tubular furnaces for use in petroleum and chemical industries for distillation, cracking and. thermal processing of various fluids. Our furnace is particularly adapted for use in the petroleum industry.

This invention is an improvement over the furnace shown in our copending application Seri No. 343,272, Vfiled June 29, 1940.

One object of our invention is to provide a furnace in which uniform heat intensity is delivered throughout the full length of all the tubes. l

Another object of our invention is to provide a furnace of high eliiciency having a convection section comprising an extension of the radiant Another object of the invention is to provide a nonrefractory furnace setting wherein a nonoxidizing, reiiective, alloy retaining plate surrounds the heat absorbing elements or tubesand is itself encompassed by suitable insulating ma-V terial positioned between the retaining plate and the outer metallic casing or shell.

Another object of our invention is to provide a. prefabricated furnace of low cost and low weight.

Another object of our invention is to provide an oil heating furnace in which the path of oil travel is reduced to the minimum, making for a low pressure drop.

Other and further objects of our invention will appear from the following description.

In the accompanying drawing which forms part of the instant specification and is to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views;

.Figure l is a sectional View of a furnace showing one embodiment of our invention Figure 2 is an enlarged sectional view of the upper portion of the convection section of our furnace.

Figure 3 is a sectional view taken on the lme 3 3 of Figure 2.

Figure 4 is a sectional view taken on the line 4-4 of Figure 2.

Referring nowto the drawing, a pedestal I supports a tube support casting 2 and a prefabrlcated metal sheathing 3.. Internal alloy sheathing 4 is spaced from the sheathing 3 and positions the insulating material. The insulating material 5 is mono-block, high temperature insulation, while the insulation Ii is rock wool blanket or the like.

Y tubes without resorting to excessive tube lengths.

are supported at the bottom of the furnace. These burners are directional, that is, the type in which theburner tips may be turned to give a swirling or tangential velocity to the iiue gas. insulating concrete 8 `and re brick 9 form the door of the combustion chamber around which the tubes I0 are positioned along the circumfer ence of a circle. Observation openings II, closed by doors IZ are provided near the base of the combustion chamber. The tubes I0 are joined at the bottom by headers I3 and at the tops by headers I4. A steam snufling pipe I5 may be provided, if desired. Adjacent the upper end of the furnace, We provide an alloy cone I6 having a cylindrical base portion Il, secured or suspended from the top of the furnace by means of bolts i8. The alloy cone serves the 'same function in the instant application as that in our copending application, Serial No. 343,272. The cylindrical base portion`i1 forms an extended convection section through which the 'flue gases pass on their-way to a stack I9. An 'annular enamel member 20 forms a guide tube sheet, permitting the tubes to expand and contract.

It will be observed that the portions of the I tubes l0 within the annular convection passageway are provided with contact ns 2I. These fins are welded to the tubes in heat exchange contact therewith. The combustion gases pass upwardly and progressively give their heat to the iins as-they pass over the tubes.' The ns are increased in area toward the tip to -compensate for the lower temperatures involved, thus maintainingthe uniform heat exchange gradient on this portion of the tubes. The ratio .of iin surface to bare tube surface is such that the entire tube operates at substantially uniform heat. For example, if the maximum permissible transfer rate is 9,000 B. t. ru. per square foot, the radiant surface is designed for these conditions and in the convection zone the ns are increased as the flue gas temperature decreases so that a rate of 9,000 B. t. u. is maintained through the entire convection section.

It will be observed that' the burner tips of the burner I are arranged to give the gas a whirling motion, due to their tangential discharge. This brings the burning gases into contact with the tubes throughout their entire length. 'I'he radiant cone I6 will be heated so that its radiant heat compensates for the drop in temperature of the combustion gases due to the giving up of some of their heat' to the iiuid being heated. The radiating area, however, increases to compensate for A plurality of oil burners 'I 55 the lowered sensible temperaturen! the combustion gases. That is, the radiation and increased velocity due to reducing the cross sectional area makes up progressively for the drop in the temperature of the combustion gases. This principle is carried on in the convection section, and the whole design is such that a uniform heat transfer exists throughout the entire length of 'the tubes Il.

The arrangement of tubes around the combustion chamber oifers a maximum of heat exchange surface within the radiant zone to the heat of the combustion gases. The construction of the furnace is such that a portion of the tubes is positioned in the radiant zone and a portion in the convection zone. 'I'hat portion in the radiant zone exposes a bare tube surface to the radiant heat of the combustion gases, while ns or ex-A tended surfaces of any suitable type are affixed to that portion of the tubes in the convection section. The amount of the extended or fin tube surface in the convection section is proportioned f and convection zones and throughout the full length of the tubes. In order to obtain this uniform heat absorption, care is taken to fire the furnace properly, direct the burners at a proper -angleand shape the fins or extended surfaces in the convection zone so that a greater amount of heat is absorbed at the discharge end where the flue gases are at their lowest temperature than at the entrance to the convection section where the flue gases contain a greater amount of heat.

It is appreciated also that, although it has been indicated that radiant heat is more or less the sole source of heat supplied to the tubes in the radiant zone, there is inevitably a. certain amount of convection heat transmitted to the tubes, due to swirling and spiral circulation of the combustion gases occasioned by the arrangement of the burners and the manner of firing the furnace.

It will be observed that the cylindrical base section I1 of the radiant cone I6 is such that it is unnecessary to use any brickwork at the top of the furnace, because the ue gas is suilciently low in temperature to be introduced directly into the stack. Thus, it is only necessary to insulate the roof 0f the base member by insulating the materiall 22, which prevents radiation losses at the top of the furnace. i

The invention as suggested heretofore, is adaptable as well to the heating of fluids such as water heaters, steam generating units and evaporators as well as for use in the petroleum and chemical industries.

It will be seen that we have accomplished the objects of our invention. We have provided a furnace in which high efficiency use of fuel is made with the full length of al1 tubes operating at the maximum possible transfer rate. A minimum path of oil travel is provided due to the therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, we claim:

1. A furnace including in combination a combustion chamber having radiant and convection zones through which combustion gases pass, a plurality of heat exchange elements positioned in said combustion chamber and having a portion thereof in the radiant zone and a portion thereof in the convection zone, said portion in the radiant zone exposing a plane surface to the combustion gases and the portion in the convection section exposing to the combustion gases a heat conducting extended surface bonded to the tubes to form an integral structure, the amount of extended surface increasing with decreasing combustion gas temperature passing thereover.

2. A furnace including in combination a combustion chamber having radiant convection zones through which combustion gases pass, a plurality of substantially vertical heat exchange tubes positioned in saidcombustion chamber and having a portion thereof in the radiant zone and a portion thereof in the convection zone, the portion in the radiant zone exposing a plane surface tothe combustion gases and the portion in the convection zone exposing a heat conducting extended surface bonded to the tubes to form an integral structure.

3. A furnace including in combination a combustion chamber having radiant convection 'zones through which combustion gases pass, a

plurality of substantially vertical heat exchange tubes positioned in said combustion chamber and having a portion thereof in the radiant zone and a portion thereof in the convection zone, the portion in the radiant zone exposing a plane surface to the combustion gases and the portion in the convection zone exposing a heat conducting extended surface bonded to the tubes to form an integral structure, said extended surface being in axial alignment with the tubes.

4. A furnace including in combination a. combustion chamber having radiant and convection zones through which combustion gases pass, a depending conical member located in the upper part of the combustion chamber partly Within the convection and partly within the radiant zones, a plurality of substantially vertical heat exposing a plane surface to the combustion gases and the portion in the convection zone exposing a heat conducting extended surface bonded to the tubes to form an integral structure.

5. A furnace including vin combination a combustion chamber having radiant convection zones through "which combustion gases pass, a plurality of substantially vertical heat exchange tubes positioned in said combustion chamber andhavf ing a portion thereof in the radiant zone and a portion thereof in the convection zone, the portion iri the radiant zone exposing a plane surface to the combustion gases and the portion in the convection zone exposing a heat conducting extended surface in the form of radial ns bonded to the tubes to form an integral structure.

JOHN W. Y THROCKMORTON. JOHN .8. WALLIS. 

